This application is related to Japanese Patent Application No. 2000-117577 filed on Apr. 19, 2000, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a hot water supply system with a heat pump cycle, in which hot water heated by the heat pump cycle is stored in a water tank to be used.
2. Description of Related Art
In a conventional heat pump cycle used for a hot water supply system, because an oil for lubricating a sliding portion of a compressor is sealed, the oil is mixed in refrigerant circulating in the heat pump cycle, and a cycle efficiency is decreased due to the oil. To overcome this problem, an oil separator for separating oil from refrigerant can be disposed at a refrigerant discharge side of the compressor so that oil separated from refrigerant in the oil separator is returned to the compressor. However, because the oil separated from refrigerant in the oil separator has a high temperature, low-temperature gas refrigerant sucked into the compressor is heated when the high-temperature oil is returned to the compressor.
More particularly, in a super-critical (trans-critical) heat pump cycle where a refrigerant pressure discharged from the compressor becomes more than the critical pressure of refrigerant, a large amount of oil is need, as compared with a general refrigerant cycle using flon as refrigerant. Accordingly, the oil heat greatly affects the super-critical heat pump-cycle.
In view of the foregoing problems, it is an object of the present invention to provide a hot water supply system with a heat pump cycle, which can improve a cycle efficiency.
According to the present invention, in a hot water supply system, a heat pump cycle includes an oil separator, disposed at a refrigerant discharge side of a compressor, for separating oil and refrigerant discharged from the compressor from each other, and a heat exchanger which is disposed to perform a heat exchange between oil separated in and flowing from the oil separator and water from a tank for storing heated water. Further, oil separated from refrigerant in the oil separator returns to the compressor after passing through the heat exchanger. Therefore, water is heated in the heat exchanger by high-temperature oil from the oil separator, and oil returning to the compressor is cooled by water, in the heat exchanger. Accordingly, oil heat can be effectively used for heating water, and a cycle efficiency of the heat pump cycle can be increased.
Preferably, a flow direction of oil is opposite to a flow direction of water in the heat exchanger. Therefore, heat exchanging efficiency between oil and water can be improved in the heat exchanger, and oil heat can be effectively recovered.
Preferably, the heat exchanger includes the first heat exchanging portion and the second heat exchanging portion which are integrally formed to have a refrigerant passage through which refrigerant flows, an oil passage through which oil flows and a water passage through which water flows. Further, the water passage is provided between the refrigerant passage and the oil passage. Accordingly, water can be effectively heat-exchanged with refrigerant and oil, respectively, and heat from refrigerant and oil can be effectively used for heating water.
When high-pressure side refrigerant pressure is equal to or greater than critical pressure of refrigerant in the heat pump cycle, an oil amount sealed in the heat pump cycle becomes larger. Even in this case, because the oil heat can be effectively recovered in the heat exchanger, heat loss can be prevented.